I did search but did not find a good answer. I have a 1975 280z FI all stock 280z. Has the EGR and catalytic converter with the warning lable on the fuel gauge "unleaded fuel only"

I have also been reading about valve seats being made from softer materials on the N42 due the running of leaded fuel (non Cali cars I assume).

So is it likely that California cars had the hard steel valve seats? Just wondering. I do run unleaded ethanol free and all seems good.

Generally people seem to say that the harder seats didn't show up until the N47 head, I think.  But Nissan does mention hardened seat materials in the 1976 Service Bulletin.  Seems like if they reported it in 1976 then the engines before probably didn't have it.  I'd say "unlikely".  

If the valves and seats wear your valve lash will close up.  That could be a maintenance check to do, to head off problems.

Edit - might as well post the words in.  Pictures below.

 

Edited October 23, 20168 yr by Zed Head

from my research that I was doing when finding parts for my motor, there were bronze seats used in the e88 heads, while the e42 head that i bought had steel seat placed into them (not sure if replaced). But according to http://datsunzgarage.com/heads/ only 2 states during the e42 run had steel seats (and cats), while the other 48 states had bronze. 

 

you could pull the head off and check 

According to the information at CarPartsManual.com all L28 engines take the same Intake and Exhaust seats, and these are steel. The actual illustration of the Valve Seats is in a weird location ( at front of head gasket ) so people often miss the listing if they only look at the picture.

Illustration #5:  Insert - Valve Intake = 11098-N4210

Illustration #6: Insert - Valve Exhaust = 11099-N6810

http://www.carpartsmanual.com/datsun/Z-1969-1978/engine-280z/cylinder-head

The following site also indicates that both L28 N42 and N47 heads came with steel Intake seats:

http://www.viczcar.com/forum/topic/4286-overview-of-l6-engine-heads/

 

Edit. I think the confusion may be that the 260Z also used an N42 head. Different part number of head for 260Z and the Intake Valve Seat part number is 11098-U8710. Vs 11098-N4210 in the 280Z N42 head. Both the 260Z and 280Z head use the same Intake Valve ( 44mm ). Might be some crossover of 260Z N42 heads to early production models of 1975 280 Z's????

Illustration #2 ( 260Z Intake seat ):

http://www.carpartsmanual.com/datsun/Z-1969-1978/engine-240z-260z/cylinder-head

Edited October 24, 20168 yr by Chickenman

That's a good find.  The N42 page, the first that you showed in Post #4, shows the intake seat changing in 6/75 (fairly close to Nissan's Bulletin), and the exhaust at 4/76.  So a 75 might have harder intake seats, but probably not exhaust.  

My 1/76 build would have the harder intakes, but soft exhaust.  I put about 20,000 miles on that engine and didn't have any problems.  I think I rechecked lash at 10,000 miles.  Seemed like it had never been off, it's out of the car now.

My L28 is a N42 with N42 head. All the valve seats are steel. I don't really know if mine came from a 75 or 76 model 280Z.